Travis: skip osx/gcc configuration
Travis: skip osx/gcc configuration

With recent osx toolchains gcc is an alias for clang.

ocelot-inc/tarantool,rtsisyk/tarantool,rtsisyk/tarantool,rtsisyk/tarantool,mejedi/tarantool,ocelot-inc/tarantool,mejedi/tarantool,ocelot-inc/tarantool,rtsisyk/tarantool,mejedi/tarantool,ocelot-inc/tarantool,mejedi/tarantool